1. Field of the Invention
This invention relates to an article having a whitened polyolefin surface, and in particular to a remarkably whitened surface of an article wherein the surface is a novel polyolefin composition.
2. Description of the Prior Art
Articles having a polyolefin surface include fibrous articles, films, molded articles and articles prepared by providing materials other than a polyolefin, such as other synthetic resins, metals, paper, ceramic products, woods, etc., with a polyolefin as a coating layer or laminate. These articles are used in many fields. For example, laminates with a synthetic resin or metal are used in utensils, household articles, e.g., a furniture, or a poster, laminates with paper are used as supports for photographic materials, various printing papers, covers for books, etc.
In certain special uses the polyolefin surface required to be white, especially in uses such as a material for a photographic support, a printing paper or a poster, and the polyolefin surface layer whitened by adding thereto a white pigment.
A very special case is that of light-sensitive materials comprising a light-sensitive emulsion layer on a support. Upon exposure to light, light is reflected by the support and the reflected light influences the exposed emulsion layer and causes deterioration in the sharpness of final photographic image. To diminish the light-reflection, various means have been used. Usually, in the case of photographic paper, the support is filled with a white pigment and made opaque. For example, photographic baryta paper has a BaSO.sub.4 -rich surface layer, and polymer films for photographic use contain white pigments such as titanium dioxide, zinc oxide, basic lead carbonate, antimony oxide, zinc sulfide, calcium sulfate, etc.
However, among these white pigments, only titanium oxide and zinc sulfide have a high refractive index to the light, and hence the polyolefin surface wherein other white pigments are used has the defect that it does not become sufficiently opaque. White zinc sulfate is excellent in its action of making the surface opaque, when applied to, for example, a photographic light-sensitive material, it has the serious defect that it causes fog on the photographic light-sensitive emulsion, and hence it cannot be applied to a light-sensitive material. Since titanium dioxide itself is not pure white, a polyolefin surface to which titanium dioxide is added has a yellowish tint and hence a polyolefin surface containing titanium dioxide has the defect that sufficient whitening effect by a fluorescent agent cannot be obtained due to the small reflectance to ultraviolet rays of wave lengths shorter than 400 m.mu.. Therefore, it is difficult to make the surface pure-white using titanium dioxide.